I have to agree with Bob2 that synonomouse is prone to senior moments - had one this morning while ruminating over where to cut in a Caltrain extension to the Eastbay out of SOMA. I was thinking large along the lines of eventually Sacramento to SOMA and then south to San Jose. And then the light came on in the dim bulb: build a half grand-union at a propitious location somewhat south of the proposed Pennsylvania Ave.(St.?)tunnel so that you can not only go south but also somewhat north.

North as right into the Transbay Terminal, or whatever it will be called in decades to come. Trains from the Eastbay right into where they used to go ca. 1940. Granted it would be tight accommodating all the trains but consider the Crazy Train to Palmdale is so poorly conceived there won't be that much business. Caltrain will be carrying most all the passengers.

The insiders are constantly kvetching we need another Bay crossing. A fortune has been spent on the Terminal structure and in turn probably something on the order of $10bil ultimately on the TBT tunnel. All you have to do is mine the second transbay tunnel-tube and wire the Capitol Corridor. By that time Ms. Schaaf may have scared the UP off anyway.

Upside of this idea is that it does not materially conflict with set-in-concrete obsessions of the power elite. You are never going to talk MTC and the SVLG out of Pacheco, no matter how dumb it is. Granted this scheme does contrary Bechtelian Imperial Gauge Manifest Destiny but that crowd has died off to the point BART finally was able to go tapered wheel profile. SPUR can be brought around as this accesses a whole new infrastructure network in the Eastbay whilst a second BART tube just taps into funky old white elephant BART. And then you have to spend a whole bunch more money to get into downtown SF with a second BART tube.